1. Field of the Invention
The present invention relates to a network device for processing data in a network and more particularly to a process of controlling the flow of data through the network device that allows for enhanced processing speeds as well as expandability.
2. Description of the Related Art
A network may include one or more network devices, such as Ethernet switches, each of which includes several modules that are used to process information that is transmitted through the device. Specifically, the device may include port interface modules, designed to send and receive data over a network, a Memory Management Unit (MMU), to store that data until it is forwarded or further processed and resolution modules, that allow the data to be reviewed and processed according to instructions. The resolution modules include switching functionalities for determining to which destination port data should be directed. One of the ports on the network device may be a CPU port that enables the device to send and receive information to and from external switching routing control entities or CPUs.
Many network devices operate as Ethernet switches, where packets enter the device from multiple ports, where switching and other processing are performed on the packets. Thereafter, the packets are transmitted to one or more destination ports through the MMU. The MMU enables sharing of packet buffer among different ports while providing resource guarantees for every ingress port, egress port and class of service queue.
According to current switching system architectures, eight class of service queues are associated with each egress port. To ensure bandwidth guarantees across the ports and queues, the device includes a scheduler that provides arbitration across the class of service queues to ensure minimum and maximum bandwidth guarantees. One implementation for ensuring bandwidth guarantees across the queues associated with each port is to assign a fixed portion of the total bandwidth for the port to each queue. As such, a queue that is associated with a class of service with a high priority may be assigned a greater fixed portion than a queue that is associated with a lower priority class of service. The scheduler then processes packets in each queue, for example in a round robin fashion.
However, such an implementation is inflexible. For example, when a queue is idle, the bandwidth assigned to that queue is unused even if another queue requires more bandwidth than the amount allocated to it. As such packets may be dropped on one queue that is exceeding its allocated bandwidth while the bandwidth of an idle queue remains unused. Therefore, there is need for improved metering and scheduling process that allow for processing of data at required speeds and provides flexibility needed to utilize all of the resources of the network device.